The present invention relates to a method of packaging a beverage containing gas in solution and to a beverage package. More particularly the invention concerns beverage packages of the kind discussed in our U.K. Patent GB-A-2,183,592 in which a sealed container is charged with beverage containing gas in solution and includes a hollow insert having a chamber which communicates with the beverage through a restricted aperture. The hollow insert contains fluid comprising gas under pressure which is in equilibrium with gas at a pressure greater than atmospheric in the headspace of the container. Upon opening the container to dispense the beverage, the headspace is opened to atmosphere which results in a pressure differential causing the pressure of gas in the insert to eject fluid (which may be gas, beverage or froth) from the insert by way of the restricted aperture. The ejected fluid is jetted into the beverage in the container and this causes gas in solution in the beverage to be liberated for the development of froth. The use of hollow inserts in beverage packages for froth development has met with considerable commercial success and since the concept of such an insert (as initially proposed in our aforementioned U.K. Patent) many forms and structures for hollow inserts have been proposed in an attempt to reduce their cost of manufacture and also processing costs for fitting the inserts into the containers. Commercially, beverage packages, typically fermented beers, which include hollow inserts (utilising so-called xe2x80x9cwidgetxe2x80x9d technology) are sold by the millions per annum so it will be appreciated that a small saving in the cost of manufacture or fitting of each hollow insert can result in a considerable overall saving per annum. One way of achieving such a saving is by reducing the amount of material required for each hollow insert and also the cost of locating the insert in its container and hollow inserts which float on the beverage lend themselves towards this. A floating insert has the advantage that it can simply be dropped into the container (or otherwise easily deposited) to save on material costs for flanges or other extensions by which the insert is intended to be wedged or otherwise secured at a predetermined position in the container and also in alleviating the requirement for specialised equipment on a filling line to locate (typically wedge) a hollow insert into its container. Where hollow inserts are wedged into a container as aforementioned it is necessary to ensure that the container walls are adequate to withstand the stresses to which they are subjected by the wedging operation. Consequently, where the hollow insert is allowed to float it may be possible to use thinner walled containers and thereby provide a further saving.
Use of hollow inserts which float on the beverage in the container and are loaded, weighted or otherwise ballasted to ensure that the restricted aperture is maintained below the surface of the beverage was originally proposed in our GB-A-2,183,592. Following from that concept many hollow inserts have been proposed, often of a spherical structure, for floating on the beverage but such latter proposals are, typically, of a somewhat expensive and complicated structure and rely upon relatively complex technology for their operation to effect in the jetting of fluid into the beverage to liberate gas from solution in the beverage and the development of froth (upon opening of the container). Examples of such hollow inserts are to be found in Patents GB-A-2,280,886, GB-A-2,280,887, International Publication WO 95/03983 and International Publication WO 95/03982. In these latter publications the hollow inserts may require a sophisticated arrangement of individual chambers and interconnecting passages, the use of non-return valves and the use of displaceable ballasting arrangements or internal wicking devices.
It is now recognised in hollow insert or xe2x80x9cwidgetxe2x80x9d technology that the fluid which is ejected from the hollow insert to initiate froth development should, preferably, be predominantly gas under pressure as this provides efficient liberation of gas from solution in the beverage (as compared with such liberation as is achieved predominantly by the ejection of liquid beverage from a floating hollow insert). Hollow inserts are well known which are initially located in the container as a sealed capsule containing gas under pressure but such pre-sealed inserts are expensive. Far less expensive is a hollow insert which derives its gas under pressure (required for ejecting into the beverage to effect froth formation) from the pressurised headspace of the sealed beverage package. With this latter proposal it is essential to ensure that when the headspace is vented to atmosphere upon opening of the beverage package, adequate pressure is available in the insert to provide the necessary pressure differential to develop the jetting effect for froth development and hence the relatively complicated structures and fluid technology employed by the hollow inserts disclosed in the four last mentioned prior Patents. More particularly, a non-return valve permits the chamber of the hollow insert to be pressurised from the headspace of the beverage package through such valve and for gas in the pressurised insert to be ejected through a further non-return valve into the beverage for froth development. The complex system of fluid flow passages and chambers together with the moving ballast and beverage wicking arrangements act so that when the chamber of the floating insert has been pressurised with gas from the headspace of the sealed package, beverage has also been taken into the insert and this causes a change in the ballast which then causes the insert to rotate during its floatation to a condition in readiness for gas to be ejected for froth formation.
It is an object of the present invention to provide a method of packaging a beverage containing gas in solution and also a beverage package of the kind generally discussed above which utilises a floating hollow insert, which will provide for efficient development of froth upon opening of the container, and which lends itself to the use of a hollow insert of a very simple structure capable of relatively inexpensive manufacture.
According to the present invention there is provided a method of packaging a beverage having gas in solution therewith which comprises providing an open topped container having a primary chamber and charging the primary chamber with the beverage to form a headspace; providing in the primary chamber a hollow insert having a secondary chamber and restricted aperture means through which the secondary chamber communicates with the primary chamber, said hollow insert being floatable on the beverage in the primary chamber and being ballasted as provided to the container to an orientation in which the restricted aperture means is at a predetermined disposition relative to the surface of the beverage when floating naturally thereon; closing the open top to seal the primary chamber and pressurising the headspace to a pressure greater than atmospheric, and which further comprises locating the hollow insert in the headspace in a raised position in which it is raised relative to its natural floating position during said pressurisation for location of the restricted aperture means in communication with the headspace and provide in the secondary chamber pressurised fluid comprising gas under pressure derived from the primary chamber and following said fluid pressurisation of the secondary chamber, locating the hollow insert in a lowered position to float naturally on the beverage with the restricted aperture means submerged in the beverage so that when the headspace is open to atmospheric pressure, a pressure differential caused by the decrease in pressure at the headspace causes fluid comprising gas under pressure in the secondary chamber to be ejected by way of the restricted aperture means to jet into the beverage of the primary chamber and said ejection causes gas in solution in the beverage to be evolved for the development of froth on the beverage.
By the present invention it is envisaged that the hollow insert as manufactured and provided to the container will have buoyancy characteristics whereby it will float naturally on the beverage and be ballasted, preferably, to an orientation in which its restricted aperture means (which may comprise one or more apertures) is submerged within the beverage. Alternatively the hollow insert may be ballasted to float naturally on the beverage with its restricted aperture means coinciding with the surface of the beverage or slightly above that surface. During pressurisation of the headspace the hollow insert is located in a raised position (that is a position in which the insert is raised relative to its position when floating naturally on the beverage) sufficiently for the restricted aperture means to communicate with the headspace (or to maintain that communication) and thereby to the gas at greater than atmospheric pressure in the headspace. With the restricted aperture means communicating with the headspace, the secondary chamber will rapidly come into equilibrium with the pressure in the headspace. Following pressurisation of the secondary chamber by gas pressure derived from the headspace of the primary chamber, the hollow insert is located in a lowered position to float naturally on the beverage with its restricted aperture means submerged. In the aforesaid arrangement in which the insert floats naturally with its restricted aperture means coinciding with, or slightly above, the surface of the beverage, it will be necessary for some beverage to be taken into the secondary chamber along with gas from the primary chamber to change the ballasting for the insert to sink slightly deeper into the beverage so that the restricted aperture means will be submerged in the lowered position. When the insert is located in its lowered position (following pressurisation of the secondary chamber) to float naturally on the beverage it is preferred that the insert is in said predetermined orientation. However it will be appreciated that when the secondary chamber takes in beverage from the primary chamber during pressurisation as aforementioned it is possible that the orientation of the insert will change slightly from the orientation it presents when floating naturally prior to pressurisation (and empty of beverage) due to a change in its ballasting caused by the inboard beverage. In its raised position it is not essential for the whole of the hollow insert to be out of the beverage. Provided that in its raised position the insert is sufficiently high relative to the surface of the beverage to expose or increase the exposure of the restricted aperture means to the headspace a bottom part of the insert can remain in the beverage (consequently the depth of the headspace need not be sufficiently large to accommodate the whole of the hollow insert). During pressurisation of the secondary chamber with the hollow insert in its raised position, it is possible (and, under certain conditions, necessary as aforementioned) that a small amount of beverage or froth (which may exist on that beverage in the primary chamber) will be drawn into the secondary chamber. Preferably however any such volume of beverage is arranged to be minimal and is preferably ejected through the restricted aperture means as fluid along with gas for the development of froth on opening of the package. By use of the teaching of the present invention it is possible to pressurise the secondary chamber so that substantially the whole of the fluid that is ejected from the secondary chamber will be a jet of gas derived from the headspace and to alleviate wastage of beverage that may be drawn into the hollow insert and not ejected back into the primary chamber to be dispensed when the package is opened.
A particularly advantageous feature of the present invention is that it lends itself to the use of a hollow insert of extremely simple structure consisting of a shell or capsule defining a single (secondary) chamber and having one or more restricted apertures extending through the shell or capsule wall to communicate with the single chamber, such a hollow insert being ballasted to a natural floating position by a loading or weighting provided by variations in thickness in the wall of the capsule or shell. Such a simple hollow insert is undoubtedly less expensive to manufacture than the prior hollow inserts of the floating type which require non-return valves, numerous chambers and internal passages, displaceable ballasting or beverage wicking arrangements. Preferably the hollow insert is spherical with its secondary chamber defined by a substantially plain internal spherical wall of the insert to be unencumbered, the sphere of the secondary chamber is eccentric with the spherical outer surface of the insert to provide for a variation in wall thickness of the insert and the varying wall thickness is arranged to provide a variation in weight per unit area that will cause the insert to be ballasted to a predetermined orientation when floating naturally on the beverage for the restricted aperture means to be disposed at a predetermined position relative to the surface of the beverage.
In accordance with the method of the present invention the hollow insert may be located in the primary chamber for that insert to float naturally on the beverage in its lowered position and subsequently raised to its raised position prior to pressurisation of the headspace. To achieve this the open topped container may be charged with its beverage and the hollow insert then located in the container to float naturally on that beverage in its lowered position prior to the insert being raised to its raised position, preferably prior to or as the headspace is being pressurised to a pressure greater than atmospheric. Alternatively the hollow insert may be located in the primary chamber prior to that chamber being charged with beverage so that the hollow insert floats on the beverage as the volume of beverage in the primary chamber increases during the formation of the headspace. The raising of the hollow insert from its lowered position when floating naturally to its raised position is preferably achieved by subjecting the insert to a horizontally directed component of force relative to the container to cause the insert to be urged into abutment with a wall of the container which results in the insert being displaced temporarily into its raised position for gas pressurisation of the secondary chamber. To facilitate raising of the insert from its lowered position to its raised position, the wall of the container may present or carry a ramp surface against which the insert abuts to be assisted thereby in moving to its raised position. Such a ramp surface may be presented by a formation in the wall of the container or by a simple angled skirt or other fitment carried within the container. It is preferred that the or a horizontally directed component of force is applied to the insert as a result of the insert being subjected to a centrifugal force following from rotation of the container. Such a centrifugal force may serve to cause the insert to abut the wall of the container as aforementioend and/or cause the insert otherwise to be displaced into its raised condition (possibly due to the development of a vortex in the beverage on which the insert floats). This centrifugal force conveniently results from rotation of the container about its own upstanding axis during sealing of its open top, for example as during a conventional seaming operation for sealing a metallic lid to the open top of an upstanding metallic can.
A less preferred technique for temporarily raising the insert from its lowered position to its raised position or for temporarily retaining the insert in its raised position whilst effecting pressurisation of the secondary chamber is to subject the insert to a vertically directed component of force by magnetic attraction. For such magnetic attraction it will be appreciated that appropriately magnetic material will have to be provided on or in the structure of the hollow insert. This magnetic technique may be particularly suitable for use with non-metallic containers such as glass or plastics bottles or cartons.
The present invention also envisages the possibility of initially locating the hollow insert in the primary chamber in its raised position and maintaining that position during pressurisation of the headspace. With this technique it is likely that the hollow insert will be located initially in its raised position in the primary chamber prior to the primary chamber being charged with the beverage. For example, a container in the form of an open topped can may be delivered to a filling line with the hollow insert already fitted in its raised position, the insert being temporarily retained on a wall of the can. Alternatively the hollow insert may be inserted into the can on the packaging line and temporarily retained at its raised position on a wall of the can for that can to move along the filling line to be charged with beverage. Usually the hollow insert will be retained temporarily on a wall of the container by a food grade adhesive and subsequently released from the adhesive to adopt its lowered position in which it floats naturally on the beverage, such release being achieved, for example, by applying heat to the container, by peristalsis of the wall of the container, or by applying an external shock force to the container as appropriate for the particular adhesive which is selected. Also the insert can be retained in its initial raised position magnetically as previously mentioned or by use of temporary tack adhesives which rapidly decay in the environment of the sealed package.
Preferably the headspace will be pressurised to a pressure greater than atmospheric by subjecting the headspace to a dose of liquid nitrogen in accordance with conventional practice. Following such dosing the open top of the container will be sealed and the contents of the container permitted to come into equilibrium. With liquid nitrogen dosing it is preferred that the insert is located in its raised position prior to or during sealing of the open top of the container and that this raised position is maintained at least until the open top of the container is sealed and substantially the whole of the liquid nitrogen has evaporated. In a conventional beer canning line using liquid nitrogen dosing, the liquid nitrogen dose evaporates extremely rapidly as a can moves towards its sealing station where the open top is closed and sealed by a seaming operation in which the can is rotated about its vertical axis. At the end of the seaming operation it is likely that a major part of the nitrogen dose will have evaporated to pressurise the headspace to a substantial proportion of its final pressure. Conventionally the can rotates about its own axis for the seaming operation and is possibly additionally rotated on a carousel during this operation, conveniently this rotation is employed to subject the hollow insert to a centrifugal force which causes it to move into its raised position in accordance with a preferred method of the present invention.
Further according to the present invention there is provided a beverage package (which package is preferably made by the method of the present invention) comprising a sealed container having a primary chamber containing beverage having gas in solution therewith and forming a headspace comprising gas at a pressure greater than atmospheric; a hollow insert floating on the beverage in the primary chamber, said insert having a secondary chamber containing fluid which comprises gas at a pressure greater than atmospheric, having restricted aperture means through which the secondary chamber communicates with the primary chamber, and being ballasted to a position in which the insert floats naturally on the beverage with the restricted aperture means submerged in the beverage; the package being openable to open the headspace to atmospheric pressure and thereby cause a pressure differential whereby fluid in the secondary chamber is ejected with a jetting effect through the restricted aperture means into the beverage in the primary chamber by the pressure of gas in the secondary chamber and said ejection causes gas in solution in the beverage to be evolved for the formation of froth on the beverage, and wherein the restricted aperture means is arranged so that the jetting effect therefrom is applied with a horizontal component of force or thrust within the beverage and said thrust causes the insert to be displaced in the beverage with a rotary motion about a substantially horizontal axis, said rotary motion resulting in the jetting effect being displaced circumferentially to penetrate deeper into the beverage in the primary chamber and thereby cause gas in solution to be evolved from the beverage over a greater depth than would otherwise be effected without said rotary motion of the insert.
Still further according to the present invention there is provided a beverage package (preferably made by the method of the present invention) comprising a sealed container having a primary chamber containing beverage having gas in solution therewith and forming a headspace comprising gas at pressure greater than atmospheric; a hollow insert floating on the beverage in the primary chamber, said insert having a secondary chamber containing fluid which comprises gas at a pressure greater than atmospheric, having restricted aperture means through which the secondary chamber communicates with the primary chamber and being ballasted to a position in which the insert floats naturally on the beverage with the restricted aperture means submerged in the beverage; the package being openable to open the headspace to atmospheric pressure and thereby cause a pressure differential whereby fluid in the secondary chamber is ejected with a jetting effect through the restricted aperture means into the beverage in the primary chamber by the pressure of gas in the secondary chamber and said ejection causes gas in solution in the beverage to be evolved for the formation of froth on the beverage, and wherein the restricted aperture means is arranged so that the jetting effect therefrom is applied with at least two horizontal components of force or thrust within the beverage and said horizontal components of thrust from the restricted aperture means are directed to restrain the insert from exhibiting rotary motion about a substantially horizontal axis and to maintain the jetting effect directed to a minor depth of the beverage in the primary chamber and thereby cause gas in solution to be evolved from beverage over a lesser depth than would otherwise be effected by deeper penetration of the jetting effect that would result from said rotary motion of the insert.
In the preferred method of the present invention where the hollow insert initially floats on the beverage in its lowered position prior to being raised to its raised position for pressurisation of the secondary chamber, it is preferred that the restricted aperture means is located at a side of the insert remote from its bottom so that, when the insert is floating naturally, the restricted aperture means is positioned slightly below or coinciding with the surface of the beveragexe2x80x94this has the advantage that the insert need only be lifted a little to move from its lowered position to its raised position. With relatively thin walled hollow inserts, particularly of the preferred spherical structure, restricted aperture means on the side of the insert will usually have a horizontally directed component of force in the jetting effect of its fluid. We have determined that for some beverages, particularly stout and ale, the characteristics are such that a relatively large evolution of gas from solution is preferred to develop a considerable froth on the beverage when the package is opened. For other beverages, particularly lager, the characteristics are such that it is preferable for a relatively small proportion of gas in solution in the beverage to be evolved when the package is opened (so that a relatively small head of froth may be provided on the beverage) whilst a considerable proportion of gas is maintained in solution in the beverage to present the beverage with a xe2x80x9csparklexe2x80x9d when it is dispensed into a drinking glass (as discussed in our U.K. Patents GB-A-2,257,107 and GB-A-2,272,201). By the beverage package of the present invention in which the hollow insert is subjected to a rotary motion about a horizontal axis by the jetting effect which is developed when the package is opened, the rotary motion of the hollow insert will displace the restricted aperture means and thereby the jetting effect so that the latter penetrates deeper into the beverage than it would otherwise do. This deep penetration can be used to liberate gas from solution in the beverage over a considerable depth of the beverage for the development of relatively large heads of froth as may be required for beverages such as stout or ale. For the beverage package of the present invention in which the restricted aperture means are disposed so that there are two or more horizontal components of force or thrust from the jetting effect within the beverage and these forces counteract each other to restrain the insert from exhibiting a rotary motion about the horizontal axis, the jetting effect may be maintained at a substantially constant depth. The evolution of gas from the beverage may thereby be restricted to a minor depth of the beverage to form a relatively small head of froth on the beverage whilst a considerable proportion of the beverage may retain its gas in solution as is considered desirable for lager.